A sample-and-hold circuit is an electronic circuit for sensing the level of a physical quantity during a short first time interval (sampling phase or observation phase) and maintaining a state indicative of the measured signal during a second time interval (hold phase) which may be longer than the first time interval. The physical quantity may, for instance, be a voltage or an electrical current. The first time interval may, in principle, be arbitrarily short, whereas the second time interval may be arbitrarily long. The level measured during the first interval may, in many cases, be considered the instantaneous level of the physical quantity in question. The measured level may also be referred to as a sample.
The state which represents the measured level may, for instance, be the electrical charge of a capacitor or a digital state. The second time interval, i.e., the period during which the sample-and-hold circuit indicates the measured level, can be used to read out the sample-and-hold circuit, i.e., transfer information representing the measured level to another device or control another device in dependence on the measured level. The second time interval can notably be used to digitize the measured level, i.e., generate a digital representation of the measured level. To this end, an analog to digital converter (ADC) may be connected to an output of the sample-and-hold circuit.
The sample-and-hold circuit may be arranged to sample the received input signals repeatedly at many instances, for instance, at a constant or variable sampling rate. The sample-and-hold circuit may thus generate a discreet set of sample values based on the received continuous or discontinuous input signal.
A sample-and-hold circuit may notably be integrated in various types of sensing devices. A sensing device may, for instance, include a capacitive, inductive, or resistive sensor element arranged to generate alone or in conjunction with other electronic components a sensor signal that may be fed to the sample-and-hold circuit.